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    <title>Document</title>
    <script>
        var num1 = prompt('请输入第一个值：');
        var num2 = prompt('请输入第二个值：');
        var num3 = prompt('请输入第三个值：');
        function gatMax(num1, num2, num3) {
            var max = 0;
            if (num1 > num2) {
                max = num1;
            } else if (num2 > num3) {
                max = num2;
            } else {
                max = num3;
            } return max;
        }
        alert('最大值为：' + gatMax(parseInt(num1), parseInt(num2), parseInt(num3)));

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